De Nora electrodic
package for Alkaline
Water Electrolysis
“Hydrogen has the potential to be a powerful
enabler of the world future energy transition “
(The Hydrogen Council – January 2017)
The importance of long lasting
energy storage technologies
Discharge time (hours)
Energy storage will become a key component of power systems in
the next decades, as the share of intermittent renewables energy
in the power mix continues to rise. Within the portfolio of storage
technologies, hydrogen is widely recognized as a promising option
for storing large quantities of renewable electricity over longer
periods.
For that reason, in a future where renewables energies (RES) will be
the dominant power source, opportunities for Power to Hydrogen
(P2H) in the long-term are acknowledged.
But hydrogen is foreseeing to be not only a media for the longPower to Gas
SNG
1000
100
Compressed
Air Storage
10
Pumped
Storage
Power to Gas
Hydrogen
1
The most established technology option for producing
hydrogen from electrical power sources is water electrolysis.
Water electrolysis will be in the future the viable alternative to
steam methane reforming + carbon capture and storage (SMR
+ CCS) for green hydrogen generation.
Month
Day
Hour
Batteries
0,1
0,01
term energy storage, it can be also the energy vector for a more
sustainable MOBILITY (through Fuel Cell Electric Vehicles - FCEV) and
a renewable feedstock for a variety of CHEMICAL PRODUCTIONS
(ammonia, methanol, green fuels, …).
Energy Storage Technologies
California Hydrogen Business Council
Flywheel
0,001
AWE Stack – courtesy of McPhy Energy (2019)
1kWh 10kWh
1MWh
1GWh
1TWh
100TWh
Storage size
SNG = Synthetic Natural Gas
(Power to Gas – Hydrogen plus methanation)
Pumped Storage = Hydro electric
Batteries = Lithium and Redox Flow
About water electrolysis technologies
and the contribution of De Nora electrodic package
Alkaline electrolyzers offer the best economics
and are likely to be dominant technology
for renewable hydrogen production to 2020;
(Bloomberg NEF: hydrogen the economics of
production from renewables – 2019)
Differently from SMR water electrolysis uses limited temperatures
and less harmful catalysts for the hydrogen generation, with
a substantial reduction of the risk level associated with this
production and a strong simplification of the production
processes (suitable for centralized of distributed generation
and characterized by lower maintenance expenses).
With a 100% RE power mix, water electrolysis can produce
GREEN HYDROGEN with zero CO2 emissions.
Three main electrolyzer technologies are used or being developed
today: Alkaline (AWE) is well established and have been used by
industry for nearly a century, proton exchange membrane (PEMWE)
is commercially available today, while Solid Oxide (SOWE) are still
in the development phase.
Both AWE and PEMWE are suitable for centralized or distributed
hydrogen (and oxygen) productions.
De Nora in the recent years spent substantial R&D efforts on AWE to
maximize its operating current density (CD) and reduce the overall
power consumption, to push this technology toward the PEMWE
performances but guaranteeing the lower CAPEX investment.
AWE electrolyzers equipped with the electrodic De Nora
package inside are able, today, to provide the lower
total cost of hydrogen (TCH) for the Power to Hydrogen
installation competitive with SMR+CCS.
Intensification of alkaline water
electrolysis – courtesy
of Nouryon (2019)
As alternative to the “package” De Nora could supply, eventually,
the active electrodes only, realized following customers proprietary
drawings and therefore easy to install inside the existing electrolysis
cells / stacks.
De Nora electrodic package
In the last decade De Nora run, also through dedicated Joint
Development Agreements with major partners, a structured project
to close the main technological drawbacks of the alkaline water
electrolysis as identified by SBC Energy Institute in the «hydrogen
based energy conversion study» (see figure below from SBC EI
2017) and other referenced studies.
The electrodic package design started from the necessity of
guaranteeing a perfect and “live” ZERO GAP configuration, able
to ensure anode and cathode contact to the diaphragm in any
operating conditions and along the overall life of the package.
In the electrodic package the cathode is always activated to reduce
the hydrogen evolving over potential, while the anode can be
In particular projects pursued the lower TCH through a activated or not, depending from the requested performances.
reduction of the overall AWE plant footprint (maximizing
the operating current density) and the optimization of
the overall power consumption (increasing efficiency and De Nora can supply to customers different combinations
operating pressure), while maintaining a low manufacturing of anode and cathode coatings as function of the electrolyzer
operating conditions, the overall required performance in terms
cost of the electrolyzer.
of cell voltage and the availability to an higher CAPEX expenditure
for obtaining the lower possible OPEX.
Case by case De Nora SALES and BUSINESS
DEVELOPMENT could assist customers in finding
the electrodes combination capable to provide, given
the specific boundary conditions, the lower TCH.
Embedded into the package De Nora could supply in addition
to the electrodes other cell internals such as: the cell bipolar
plates, the anode/cathode separator (membrane or diaphragm)
and the related gasketing system (between the separator and
the cell frames).
High Current Densities reduce the stack foot print, allowing a substantial CAPEX
cost reduction to our customers that could also benefit of good OPEX costs;
Product description
Cathode
Separator
Anode
DEA diaphragm electrode assembling composed by:
Separator
Diaphragm
AGFA Zirfon Perl UTP 500/220
https://www.agfa.com/specialty-products/solutions/membranes/zirfon/
Flow Fields
Elastic element for ZG configuration
Ni mattress; (type and thickness/shape depend from the cell geometry and must be designed case
by case by the DN’s team);
Cathode
Gaskets
Flow Field
De Nora’s electrodic package push Alkaline
Water Electrolysis toward PEM Water Electrolysis
performances, allowing the best TCH (Total Cost
of Hydrogen)
Activated mesh
Ni Flynet activated NRG®; Proprietary De Nora coating originally developed for the membrane chlor alkali
market, with whit a huge installed base (100.000 m2) and proven > 8 years lifetime;
http://www.denora.com/products/cathodes.html
Anode
Nickel mesh
Ni flynet non-activated; (the “standard” package uses a simple nickel net as electrode).
Different types of anode coating are available and can be used to reach higher cell performances;
Other parts
Gaskets (between separator and cell frame);
Bipolar plates (if requested);
Operating Conditions
Electrolyte
KOH or NaOH (25 ÷ 30% w/w);
Temperature
70 ÷ 80°C (design) or higher depending from the STACK / BOP (balance of plant) design temperature;
Pressure
Up to 60 bar(g) (design) depending from the STACK/BOP design pressure;
Delta Pressure
0.2 bar (design) differential pressure between anodic and cathodic chambers;
Circulation
Forced or natural (gas lifting), depending from the design Current Density (CD), Cell Voltage, (CV) and
the operating pressure; Normally the electrolyte circulation configuration and its flow rate are defined in
collaboration with our experts to limit the ΔT (delta temperature) through the cell < 15°C;
Current Density
Up to 12 kA/m2
Performance
(expected)
Guaranteed performances on cathode HOV (Hydrogen
Over Voltage) and anode OOV (Oxygen Over Voltage)
will be provided specifically based on the customer plant
configuration by our experts
Electrodes coating life time :
Electrodes coating life time: > 5 years (#, ##)
(#)
Electrodic package life time indicated above refers
to a current density of 9 kA/m2. In case of
a higher current density (up to 10 kA/m2)
and / or a required lifetime period beyond 5 years,
the subject should be discussed in detail with De Nora
specialists;
(##) The acceptable number of unprotected shut down
(complete system shut down, no load fluctuation)
per day should be discussed and agreed between
the customer and De Nora because impacting on
the coating solution choice;
Electrodes coating performances drift:
Cathode performance drift: < 0,5 % / Year
Anode performance drift: < 0,5 % / Year
Parameters affecting the cathode coating performances decay are:
• Operating current density (CD);
• Pollutants concentration in the electrolyte loop;
• Number of starts / stop in unprotected (no polarized) conditions;
Installation of De Nora package into an existing AWE cell architecture can increase
the operating CD by more than two times, maintaining or even reducing the cell voltage
Electrolyte LOOP quality
Gas quality
The table below shows the maximum allowable critical
pollutants concentration to keep in the electrolyte loop to
reach the higher performance and longer life of the package:
Gas quality is impacted by three factors: oxygen and hydrogen
permeation through the diaphragm, cross contamination through
the diaphragm sealing system and gas dissolved in the electrolyte
loop.
The first point relates solely to the diaphragm performance, while
the third to the system/BOP configuration: single or dual electrolyte
circulation typically.
Component (cations)
Conc.
Unit
Iron
200
ppb (w/w)
Chromium
5
ppm (w/w)
Calcium/Magnesium
10
ppm
Chloride
100
ppm (w/w)
Carbonate
10.000
ppm (w/w)
Silica
20
ppm (w/w)
Sulphate
1.000
ppm (w/w)
Demi water quality
The table above indirectly determine the feed demi water
quality. A simple material balance of the system, considering
the initial KOH purity, the BOP material corrosion rate and
the demi water feed quality, should close (at the end of the
expected electrodes life) on the pollutants concentrations
value reported in the table.
More details on feed water quality and maximum allowable
pollutants concentration in the electrolyte loop could be
provided by our experts on request.
The second point have been addressed by De Nora designing
a dedicated gasketing system for the package able to strongly limit
the cross of hydrogen and oxygen between the diaphragm and
cell frame during normal operations.
Services
Thanks to its global footprint De Nora can guarantee
the supply of new electrodes or electrodic packages and
maintenance / refurbishment services, almost in any country
around the world.
Country
References:
De Nora Italy:
Europe and Africa
Asia and China
Japan
America
Corporate (Italy)
gaetano.porcino@denora.com
simone.tremolada@denora.com
De Nora China:
andrea.cremonesi@denora.com
De Nora Japan:
andrea.cremonesi@denora.com
De Nora North America:
chuck.shultz@denora.com
De Nora Corporate:
michele.sponchiado@denora.com
AWE Stack – courtesy of tkUCE (2020)
AWE Stack – courtesy of McPhy Energy (2019)
AWE Stack – courtesy of tkUCE (2020)
WATER ELECTROLYSIS
info.dnd@denora.com
marketing@denora.com
www.denora.com
© Copyright 2016 Industrie De Nora S.p.A. - All rights reserved.
De Nora, ON circle, Our research - your future, electrochemistry at your service (and any other trademark
name) are trademarks or registered trademarks of Industrie De Nora S.p.A. in Europe and/or other
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The information contained herein is offered for use by technically qualified personnel at their discretion
and risk without warranty of any kind.
DN-Etek-04/2016